Insisting that your bike is assembled correctly is not being a D**K. Your LBS has a responsibility to you as a customer. The fact that it may have been assembled by someone else does not change that responsibility. That being said, mistakes can happen and I am glad you were not injured.
This is one of SO's favorite pictures.
"The bicycle was the first machine to redefine successfully the notion of what is feminine. The bicycle came to symbolize something very precious to women - their independence."—Sally Fox